Pull downs are driven purely by effort (ST) on a potential drop down (where you get the back up message), not a magical cycle. They just lower their expectations and "drop" to you eventually, notifying you when it happens.

If you called a D2 guy and they ignored your call, laughed at you, and/or didn't give you a "backup" message, you'll never be able to pull them down. And, not all recruits that gave you a backup message will drop-most will, but it's not 100%.